Dispersants containing terminal acidic groups such as phosphates and sulphates are known and are generally prepared by reaction of a hydroxy ended polymer chain with a phosphorylating agent such as phosphorus pentoxide, phosphorus oxychloride, phosphorus trichloride and pentachloride, polyphosphoric acid or sulphuric acid, respectively. The polymer chains are usually polyester or polyalkoxylate chains containing terminal hydroxyl groups.
U.S. Pat. No. 5,300,255 discloses dispersants containing a polyester derived from a hydroxycarboxylic acid with not more than 8 carbon atoms reacted with phosphorus pentoxide or sulphuric acid. The dispersants are useful in non-polar media, such as aromatic solvents and plastics.
U.S. Pat. No. 5,130,463 discloses dispersants containing a polyether/polyester derived from ε-caprolactone reacted with polyphosphoric acid. The dispersants are useful in a polar medium, such as ketones and esters.
U.S. Pat. No. 6,051,627 discloses dispersants including a polyether derived from ethylene oxide and propylene oxide reacted with polyphosphoric acid. The dispersants are useful in a polar medium such as ketones, esters and water.
U.S. Pat. Nos. 5,464,895 and 5,412,139 both disclose polyaryl organophosphate dispersing agents.
U.S. Pat. Nos. 2,213,477; 2,454,542; 3,004,056; 3,235,627; 4,720,514; 4,872,916; and 5,914,072 all disclose polyalkoxylates containing terminal hydroxyl groups that have been reacted with various phosphorylating agents.
International Patent Application WO 05/085261 discloses phosphated dispersants comprising a polyether/polyester chains reacted with a hydroxy di-, tri- or multi-carboxylic acid.
However, it would be advantageous to utilize the dispersant properties of compounds containing terminal acidic groups in both a polar and a non-polar organic medium. Consequently, dispersants are sought which can disperse a particulate solid in both a polar and a non-polar organic medium.